Waste heat boilers are commonly employed in manufacturing plants to recover heat from exhaust gases produced in high temperature processes such as steam reforming, catalytic cracking, coal gasification, power turbine operations, and the like. Water tube waste heat boilers typically comprise shell and tube heat exchangers wherein the hot incoming exhaust gas is directed to the shell side. Boiler water flowing through the tube side is heated and partially vaporized.
The tubes of such high temperature heat exchangers are subject to failure when the mechanical integrity of the wall is undermined by factors such as corrosion, scaling or fouling from low quality boiler water and by erosion due to the impinging inlet gas. For example, tube-side fouling increases the tube wall temperature which, in severe cases, can result in tube failure due to overheating. Severity of the operating conditions, including excessive heat flux, can exacerbate integrity problems and increase sensitivity to changes in the quality of boiler water.
The reliability of the waste heat boiler can be significantly improved even in circumstances where the boiler water quality fluctuates by addressing the problem of excessive heat flux distribution and impingement, particularly, on the outermost tubes closest to the hot gas inlet.